A Survey of Digital Rights Management Technologies http://www.cse.wustl.edu/~jain/cse571-11/ftp/drm/index.html Xiao Zhang, [email protected] (A project report written under the guidance of Prof. Raj Jain) Download Abstract: Digital Rights Management (DRM) refers to a broad category of access control technologies aimed at restricting the use and copy of digital content on a wide range of devices. We examine some recent and existing technologies that represent the standards of commercial DRM in most of mainstream media formats including film, e-book, broadcast TV, computer games and music. We discuss the architectures of these systems and their real world adoption and performances. We also look at some of the common pitfalls of DRM technologies and the attempts at building better systems. Keywords: Digital Rights Management, DRM, content, distribution, permission, metadata, restricted, protected, e-books, Blu-ray, HD-DVD, Advanced Access Content System, watermark, encryption, decryption, cryptography, Steam, Sony, OpenMG, Apple, FairPlay, Adobe, analog hole, PDF, piracy, FCC, lawsuit, EFF, Mobipocket, Topaz, Ereader, Microsoft, AACS, SecuROM, StarForce, vulnerability, incompatibility Table of Contents: 1. Introduction 2. Recent and Existing Technologies 2.1 Film Media 2.1.1 Windows Vista Protected Media Path 2.1.2 Advanced Access Content System 2.1.3 Watermarks 2.2 Broadcast TV 2.2.1 Content Protection and Copy Management 2.3 E-books 2.3.1 Adobe Adept DRM 2.3.2 Apple FairPlay 2.3.3 Mobipocket and Topaz 2.3.4 Microsoft eReader 2.4 Computer Games 2.4.1 SecuROM 2.4.2 Ubisoft Uplay 2.4.3 StarForce 2.4.4 Steam 2.5 Music 2.5.1 Sony OpenMG 2.5.2 Apple FairPlay (iTunes) 3. Vulnerabilities 3.1 Bypass of DRM Technologies 3.2 DRM and Cryptography 3.3 Incompatibility 4. Conclusion 1. Introduction The term "Digital Rights Management" (DRM) is confusing and dividing in today's world. For publishers and rights holders, it can refer to all technologies that protect them from piracy. For the average content consumer, it usually means extraneous mechanisms that cause them inconvenience in normal use. For the pirates, it means the enemy that must be vilified and destroyed. But what exactly is this technology and what does it do? DRM is defined as a broad range of technologies that grant control and protection to content providers over their own digital media. From the content's point of view, there are three key components to its life cycle: the creation of content, the distribution and upkeep of content, and the use of content. A good DRM scheme should account for all three components, and effectively define the interactions between the user, the permissions and the content itself. Figure 1 demonstrates this in more details. 1 of 10 A Survey of Digital Rights Management Technologies http://www.cse.wustl.edu/~jain/cse571-11/ftp/drm/index.html Figure 1. DRM functional architecture When contents are created, the system needs to immediately ensure that rights are validated, assigned and approved to their owners. In the distribution and storage of content, the system needs to have proper access to the content and metadata, and manages the license and deals. After content has been traded, the system must enforce the rights associated with the content, by providing proper permissions to access, use and modification [Boucqueau07]. A main issue for DRM is the lack of standardized technologies. Furthermore, many traditional DRM technologies have been plagued by usability and legal problems, or suffer from attacks that render them completely useless. As a result, many publishers in the industry developed their own proprietary software to meet the individual needs of DRM in today's media standards. In section 2, we will examine some existing as well as some recently retired technologies to understand the challenge in managing digital rights. Some of these systems, while trying to accomplish the goals of rights management, negatively affected the user experience in many ways, prompted controversies and criticisms among their customers. We will briefly discuss these here as well. Section 3 examines some general vulnerabilities of DRM systems, as well as the progress and attempts in designing better systems. 2. Recent and Existing Technologies In the past decade, many DRM technologies have been developed within the industry, but very few have survived over the years. At its core, designing a DRM system is hard; the fundamental challenge lies in the fact that the system must exist on top of the media format itself. Different media formats have vastly different distribution, content creation, metadata and scopes of permissions. They pose different challenges in very different domains. We will examine some of the most popular commercial DRM schemes in film, broadcast TV, e-books, games and music. 2.1. Film Media In the early days of DVD technologies, a DRM system called Content Scrambling System (CSS) was developed by the DVD Forum on film DVDs. It uses a simple encryption scheme designed to prevent byte-for-byte copying of a MPEG (digital video) stream. The key for the encryption is split and separately stored in the lead-in area of the restricted DVD and the DVD drive itself, and the encryption algorithm employs a proprietary 40-bit stream cipher [Schneier99]. The technology was first introduced in 1996, and was compromised in 1999 by a brute force attack. Like many other encryption algorithms before it at the time, the weakness of the scheme was blamed on the regulations placed on any exportation of cryptographic systems from the United States which limited systems to use keys of no more than 40-bit long [Schneier99][Grimmett01]. More recently, due to the rapid adoption of new media technologies such as HD-DVD and Blu-ray, new DRM systems today concern mostly with these platforms. 2.1.1. Windows Vista Protected Media Path To the dismay of the anti-DRM advocates, Microsoft introduced many new I/O technologies into their new generation of OS in late 2006. Among them is Protected Media Path (PMP), a set of technologies designed to add a layer of access control to video and audio streams. It consists of two main subsets, Protected Video Path (PVP) and Protected User Mode Audio (PUMA). Windows Vista uses something called the Protected Media Path - Output Protection Management (PMP-OPM), It is a redesign over the Certified Output Protection Protocol (COPP) introduced in Windows XP. PMP-OPM monitors all processes that access and produce media signals. A subset of PVP called User-Accessible Bus (PVP-UAB) encrypts video and audio data that are passed through the PCI-E bus, protecting it from any illegal interception before it reaches the graphics card. When a software process tries to access a DRM-restricted video stream, PVP will first check if the software is signed by Microsoft. If the process is unsigned, the access is automatically rejected. Even if a process is able to intercept the stream, it will not be able to use it due to the encryption [Ionescu07]. Protected Media Path has a crucial requirement that the graphics driver must have a way to identify whether the hardware is trustworthy - that is, if the device is allowed to play video with copy protection. There is a clear implication to this requirement: the driver must be signed by Microsoft in order to playback protected content. This has attracted criticism from the open source community speculating that PMP would affect the development of official free/open source graphics drivers from their manufacturers. Furthermore, it has been demonstrated that one can bypass the DRM check altogether by using 2 of 10 A Survey of Digital Rights Management Technologies http://www.cse.wustl.edu/~jain/cse571-11/ftp/drm/index.html specialized drivers [Ionescu07]. 2.1.2. Advanced Access Content System A cryptographic system that adds copy protection to HD DVD and Blu-ray Disc (BD) has been developed by the AACS Licensing Administrator (AACS LA), which consists of an assortment of publishers including Disney, IBM, Intel, Microsoft, Panasonic, Sony, Toshiba, and Warner Bros.. The system features several nested layers of encryption and a robust revocation system, as well as a sophisticated key generation process. Figure 2 shows the AACS system in details. Figure 2. Advanced Access Content System (AACS) There are three parts to the AACS scheme: copy protection, modification/decryption protection, and renewability/revocation. AACS prevents exact copying by using the Volume ID (VID) and a special key to let the drive handle this VID. To decrypt a disc, the user needs to acquire the Volume Unique Keys, which consists of the Volume ID and the processed device key. The device key is processed through the subset/difference tree system. Note that unlike CSS, where all players of a given model are controlled by the same shared decryption key, AACS provides each individual playback device with its unique set of decryption keys through a broadcast scheme. This enables licensors to revoke individual players by invalidating the decryption keys associated with the player. Therefore, if a given player's keys are compromised and published, the AACS LA can simply revoke those keys in any future content, making the keys and player useless for decrypting new titles. This is what the subset/difference tree system accomplishes. The resulting key, called the media key (Km), combined with the volume ID (VID) are then run through a one-way encryption scheme (AES-G) to yield the volume unique key (Kvu) needed to decrypt the title key(s). The decrypted title key (Kt) can then be used to decrypt the content [Doom9]. AACS allows for a system called "managed copy" where consumers can make legal copies of the discs they have purchased.